The Metcal soldering stations consist of an RF power source, iron, and stand. Temperature is controlled by the tip. You can buy 500C, 600C, 700C, etc tips and you just swap them when you need different temperatures.
The PS2E is a power source and is the predecessor to the MX500. Its typically the best deal in Metcal irons that you will find on ebay. Through a few different auctions I picked up a PS2E, iron, stand, and a number of different temperaturs tips and I probably spent about $150. Well worth the money.